Electrically controlled, i.e. solenoid, poppet valves are used extensively for remotely controlling large hydraulically controlled valves or actuators which will in turn control hydraulic motors, pumps or pistons or for relieving or maintaining a pre-set pressure or flow in a hydraulic system.
Such valves generally include cylindrical valve members movable on an axis in a valve cavity, the high pressure inlet port being through a side of the cavity and the outlet port being through an end of the cavity. High pressure in the cavity biases the valve member to the valve closed position with a force proportional to the area of the valve seat surrounding the outlet port. A solenoid coil surrounding the housing exerts a magnetic force on a magnetically permeable armature inside the cavity to move the valve member against the pressure bias to open the outlet port. Alternatively, a spring biases the valve member to an open position and the magnetic force moves the valve member against the spring bias to close the valve.
Such valves typically have a flow rate of from approximately one-fifth to five gallons per minute at 3,000 pounds psi pressure with a 50 pound psi pressure drop and have external dimensions in excess of 3.0 inches long and 1.0 inches in diameter.
One problem with such valves, which the present invention brings out, is the amount of axial magnetic force which must be developed in order to open the valve against the pressure forces and the inefficient magnetic circuitry used to produce this force. Further high forces are required to move the armature against the mechanical friction developed between the armature and its housing caused by unbalanced magnetic radial forces on the armature. As the magnetic forces are increased to overcome the pressure forces, the friction forces opposing such movement increase in direct ratio to the axial magnetic forces. The large internal forces which must overcome require a solenoid coil and an armature of substantial size, making the design of a miniature poppet valve extremely difficult. The inefficient magnetic circuit requires a higher than necessary number of ampere turns on the solenoid to produce the required force.
All of this either taken alone or in summation requires relatively high electrical power to energize the solenoid, making it somewhat difficult to operate the valve under control of computers or other sophisticated electrical control apparatus. Also, the physical size of the coil is increased with no benefits in end results.
A further problem with such valves, which the present invention brings out, is that the design requires that the housing and the valve member and the armature all be machined from larger pieces of metal with the valve and sealing surfaces honed to accurate dimension, an expensive manufacturing process and resulting in a further increase of bulk in the ultimate valve.